Absorbent articles for personal hygiene of the type indicated above are designed to absorb and contain body exudates, in particular large quantity of urine. These absorbent articles comprise several layers providing different functions, for example a topsheet, a backsheet and in-between an absorbent core, among other layers. The function of the absorbent core is typically to absorb and retain the exudates for a prolonged amount of time, minimize re-wet to keep the wearer dry and avoid soiling of clothes or bed sheets.
The majority of currently marketed absorbent articles comprise as absorbent material a blend of comminuted wood pulp with superabsorbent polymers (SAP) in particulate form, also called absorbent gelling materials (AGM), see for example U.S. Pat. No. 5,151,092 (Buell). Absorbent articles having a core consisting essentially of SAP as absorbent material (so called “airfelt-free” cores) have also been proposed (see e.g. U.S. Pat. No. 6,790,798 (Suzuki), WO2008/155699 (Hundorf), WO95/11652 (Tanzer), WO2012/052172 (Van Malderen)). Absorbent cores with slits or grooves have also been proposed, typically to increase the fluid acquisition properties of the core or to act as a folding guide.
The immobilization of the SAP within the core, in both wet and dry state, can be a particular challenge for absorbent articles having airfelt-free cores. U.S. Pat. No. 6,790,798 (Suzuki) and WO 2008/155699 (Hundorf) disclose absorbent cores with a patterned layer of SAP immobilized by depositing a layer of fibrous thermoplastic adhesive material over the layer of SAP. The fibrous thermoplastic material helps to maintain the position of the SAP in the absorbent core prior to and during use of the article, without substantially restricting the ability of the SAP to absorb large volumes of urine.
WO2012/170778 (Rosati et al., see also WO2012/170779, WO2012/170781 and WO2012/170808) discloses absorbent structures that comprise superabsorbent polymers, optionally a cellulosic material, and at least a pair of substantially longitudinally extending channels. The core wrap can be adhesively bonded through the channels to form a channel bond. The channel bonds may be permanent, so that their integrity is at least partially maintained both in dry and wet state. As the absorbent structure absorbs liquid and swells, the absorbent structure takes a three-dimensional shape with the channels becoming visible. The channels are indicated to provide improved fit and/or better liquid acquisition/transportation, and/or improved performance throughout the use of the absorbent structure. In some preferred embodiments, the core includes a first adhesive material applied to the absorbent layer, preferably said first adhesive material being a thermoplastic fibrous adhesive material, and a second adhesive material may be present between the supporting sheet and the absorbent layer.
While the absorbent cores of the prior art generally have good properties, there is a continuous need to reduce the usage of raw material, in particular adhesive material, while improving or at least maintaining key properties such as SAP immobilization and fluid acquisition.